fixed crash when file contains no valid frames #601

rendering/cacher.cpp

@@ -668,7 +668,7 @@ void Cacher::CacheVideoWorker() {
           qWarning() << clip->name() << "frame had no PTS value";
           av_frame_free(&decoded_frame);
 
-          if (retrieve_code == AVERROR_EOF && retrieved_frame == nullptr) {
+          if (retrieve_code == AVERROR_EOF && retrieved_frame == nullptr && !queue.isEmpty()) {
             // if we reached the end of the file, it's not an error but there are no more frames to retrieve
             // some formats EOF before the end of the duration that Olive calculates. In this event, we simply
             // return the last frame we retrieved

rendering/clipqueue.cpp

@@ -93,3 +93,8 @@ int ClipQueue::size()
 {
   return queue.size();
 }
+
+bool ClipQueue::isEmpty()
+{
+  return queue.isEmpty();
+}

rendering/clipqueue.h

@@ -159,6 +159,15 @@ public:
    */
   int size();
 
+  /**
+   * @brief Returns whether the queue is empty of not.
+   *
+   * @return
+   *
+   * **TRUE** if the queue is empty and contains no frames, **FALSE** if not.
+   */
+  bool isEmpty();
+
 private:
   QVector<AVFrame*> queue;
   QMutex queue_lock;